1. Field of the Invention
The present invention relates to a press machine environment, and, more particularly, to a method and apparatus for measuring and evaluating energy consumption and work production, specifically as a function of slide displacement during the work stroke of a press machine operating cycle.
2. Description of the Related Art
Mechanical presses of the type performing stamping and drawing operations employ a conventional construction having a movable slide guided by a frame structure including a crown and a bed. The frame structure supports the slide in a manner enabling reciprocating movement of the slide towards and away from the bed. The slide is driven by a crankshaft using a connecting arm assembly coupled to the slide. Press machines are widely used for a variety of workpiece operations and employ a large selection of die sets. Accordingly, press machines vary considerably in size and available tonnage depending upon its intended use.
A flywheel and clutch assembly are utilized to transmit mechanical energy from a main drive motor to the presscrankshaft. The flywheel assembly serves as the primary source of stored mechanical energy and rotary driving power. Standard press configurations have the flywheel located between the main drive motor and clutch, with the flywheel being mounted on either the driveshaft, crankshaft or press frame by use of a quill.
The main drive motor replenishes the flywheel with rotational energy as it becomes depleted during the course of press working strokes, namely, as the clutch engages the flywheel and establishes a driving connection between the flywheel and the crankshaft. In particular, when the crankshaft and flywheel are engaged in driving relationship, the flywheel energy is converted into mechanical work to power the press components, namely, the reciprocating slide. During engagement of the clutch, the flywheel drops in speed as the press driven parts are brought up to running speed. Press machine performance typically is described in terms of tonnage, which refers to the load developed by the press machine. However, for purposes of determining the efficiency of press machine operation, tonnage reveals nothing more than the compressive force applied to the die workpiece and therefore provides no indication as to the proportion of actual energy converted into usable work. There is needed an improved metric for describing energy consumption that better reflects the energy yield, namely, the efficiency of transferring energy from the flywheel to work in the form of workpiece processing activity.
In particular, according to the invention, machine efficiency may be investigated by determining the amount of available energy that is converted into actual useful work, e.g., die processing. During press operation, energy is extracted from the flywheel to drive the slide and develop a corresponding tonnage or load that is applied to the workpiece. Accordingly, a comparison can be made between the energy generated by the flywheel and the amount of energy applied to the workpiece as die processing (e.g., work). During the working stroke, the flywheel experiences a gradual decrease in speed as the slide gains speed while it advances towards its machining engagement with the workpiece.